1. Technical Field
The present invention relates to a development system for developing an electrostatic latent image formed on a photoconductor with developer in which toner particles are dispersed into carrier liquid and relates to an image forming apparatus using the same.
2. Related Art
In an electrophotographic development system using a liquid developer, there has been conventionally known a technology for adjusting the amount of the carrier liquid. Specifically, the liquid removing force of a sweep roller is varied based on the property of a transfer paper by an eccentric cam or the like so as to remove excess liquid developer by a suitable amount, thereby regulating a liquid film. Since the sweep roller abuts on a photoconductor drum, high-viscosity and high-concentration liquid developer which is hardly removed is easily removed and the mechanical accuracy of the sweep roller and the photoconductor drum is easily maintained (see JP-A-2003-91161).
Also in an electrophotographic development system using a liquid developer, there has been conventionally known a technology of adjusting the concentration of a liquid developer. FIG. 10 is a conventional concentration adjusting apparatus. Numeral 100 designates the concentration adjusting apparatus, 101 designates a developer inlet, 102 designates a developer concentration adjusting tank, 103 designates a motor, 104 designates a sleeve, 105 designates a first developer drain passage, 106 designates a collection tank, and 107 designates a second developer drain passage.
In the concentration adjusting apparatus 100, a liquid developer is injected into the developer concentration adjusting tank 102 through the developer inlet 101. The motor 103 is driven to exert centrifugal force on the liquid developer to form a distribution of concentration of toner having low concentration in the vicinity of the rotation center and high concentration in the vicinity of the sleeve 104 in the developer concentration adjusting tank 102. The low-concentration liquid developer in the vicinity of the rotation center is drawn through the first developer drain passage 105. On the other hand, the high-concentration liquid developer is scattered through an opening of the sleeve 104 and drawn through the second developer drain passage 107 at the bottom of the collection tank 106. That is, desired high-concentration liquid developer and desired low-concentration liquid developer can be drawn. Using the drawn developers allows the concentration control (see JP-A-10-282796).
However, JP-A-2003-91161 has a problem when a transfer paper or the like having rough surface is set. Because a larger amount of developer is required to adhere when such a paper is set, the sweep roller is spaced apart from the photoconductor drum. In this state, the sweep roller does not remove excess liquid carrier from the developer layer formed on the photoconductor drum. When a transfer paper having rough surface is set and the developer contains a large amount of liquid carrier, toner particles are drawn by fibers of the transfer paper together with the liquid carrier so as not to obtain a desired concentration. In addition, JP-A-10-282796 has a problem when a developer supplying roller with grooves such as an anilox roller is employed. Because the grooves are clogged with toner particles when the concentration of the developer is increased, it is impossible to measure the thickness of the film with accuracy.